• Title, Summary, Keyword: capacitive deionization

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COMPUTATIONAL STUDY FOR PERFORMANCE EVALUATION OF FLOW CHANNELS INSIDE CDI UNIT CELL (수치모사를 이용한 CDI Unit Cell 내부의 유로성능 평가)

  • Sohn, D.Y.;Choi, Y.H.;Park, D.W.;Jung, C.H.
    • Journal of computational fluids engineering
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    • v.15 no.1
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    • pp.31-36
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    • 2010
  • In the present study, computations for flow fields inside the CDI unit cells with electrodes and spacers have been made to evaluate their performance. Three types of unit cells that include a planar type, a serpentine channel type, and a spiral wound type were considered and their flow characteristics were compared. From the computational results, it is found that the serpentine channel type has a large flow resistance and can not guarantee the outflow flux for industrial applications. On the other hand, the planar type can sustain a large enough outflow flux but it's efficiency is low for the electrode-use because of the non-uniform velocity distribution inside the cell and dead zones in every corner. Finally, The spiral wound type has not only a large outflow flux as much as the planar type has, but also a high efficiency for the electrode-use because of uniform velocity distribution. From this comparison, we can expect that the spiral wound type of CDI unit cell would have a high performance deionization capability.

Performance of Membrane Capacitive Deionization Process Using Polyvinylidene Fluoride Heterogeneous Ion Exchange Membranes Part I : Preparation and Characterization of Heterogeneous Ion Exchange Membranes (폴리비닐플루오라이드 불균질 이온교환막을 이용한 막 결합형 축전식탈염공정의 탈염 성능 Part I : 불균질 이온교환막의 제조 및 특성)

  • Park, Cheol Oh;Rhim, Ji Won
    • Membrane Journal
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    • v.27 no.1
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    • pp.84-91
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    • 2017
  • In this study, heterogeneous ion exchange membranes were prepared by mixing cation or anion exchange resins and commercial polyvinylidene fluoride (PVDF) for MCDI process. The mixing ratios of PVDF and ion exchange resins were 1 : 1, 1.4 : 1, 2 : 1, and 3 : 1. We characterized SEM, water content, ion exchange capacity, methanol permeability, and ion conductivity. In the viewpoint of membrane characterization, the blending ratio of 2 : 1 showed the best. For the blending ratio of 2 : 1, heterogeneous cation exchange membrane showed the water content 34%, ion exchange capacity 1.54 meq/g, ion conductivity 0.019 S/cm, and methanol permeability $2.28{\times}10^{-7}{\sim}8.86{\times}10^{-7}cm^2/s$ while In the case of heterogeneous anion exchange membrane, the result showed 37%, 2.18 meq/g, and 0.034 S/cm and $1.46{\times}10^{-7}{\sim}8.66{\times}10^{-7}cm^2/s$.

Synthesis and Characteristics of Partially Fluorinated Poly(vinylidene fluroide)(PVDF) Cation Exchange Membrane via Direct Sulfonation (직접술폰화반응에 의한 부분불소화 Poly(vinylidene fluroide)(PVDF) 양이온교환막의 합성 및 특성)

  • Kang, Ki Won;Hwang, Taek Sung
    • Membrane Journal
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    • v.25 no.5
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    • pp.406-414
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    • 2015
  • In this study, partially fluorinated cation exchange membranes were prepared by direct sulfonation of Poly(VDF-co-hexafluoropropylene) copolymers (PVDF-co-HFP) followed by a casting method for application in the Membrane capacitive deionization (MCDI). The structure of sulfonated PVDF-co-HFP (SPVDF) was confirmed by Fourier-transform infrared (FT-IR) and $^1H$ Nuclear magnetic resonance ($^1H$ NMR) analysis. For quantitative analysis of the chemical composition, the X-ray Photoelectron Spectroscopy (XPS) was used. The membrane properties such as water uptake, ion exchange capacity and electrical resistance were measured. It was suggested that the optimum direct sulfonation condition of PVDF-co-HFP ion exchange membranes was $60^{\circ}C$ and 7 hours for temperature and duration of sulfonation, respectively. The water uptake of the SPVDF ion exchange membrane was 21.5%. The ion exchange capacity and electrical resistance were 0.89 meq/g and $3.70{\Omega}{\cdot}cm^2$, respectively. It was investigated that if it is feasible to apply these membranes in MCDI at various cell potentials (0.9~1.5 V) and initial flow rates (10~40 mL/min). In the MCDI process, the maximum salt removal rate was 62.5% in repeated absorption-desorption cycles.

Preparation of Highly Tough Ethylene Vinyl Acetate (EVA) Heterogeneous Cation Exchange Membranes and Their Properties of Desalination

  • Kim, In Sik;Ko, Dae Young;Canlier, Ali;Hwang, Taek Sung
    • Korean Chemical Engineering Research
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    • v.56 no.3
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    • pp.361-369
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    • 2018
  • A manufacturing method has been devised to prepare novel heterogeneous cation exchange membranes by mixing ethylene vinyl acetate (EVA) copolymers with a commercial cation exchange resin. Optimum material characteristics, mixture ratios and manufacturing conditions have been worked out for achieving favorable membrane performance. Ion exchange capacity, electrical resistance, water uptake, swelling ratio and tensile strength properties were measured. SEM analysis was used to monitor morphology. Effects of vinyl acetate (VA) content, melt index (MI) and ion exchange resin content on properties of heterogeneous cation exchange membranes have been discussed. An application test was carried out by mounting a selected membrane in a membrane capacitive deionization (MCDI) system to investigate its desalination capability. 0.92 meq/g of ion exchange capacity, $8.7{\Omega}.cm^2$ of electrical resistance, $40kgf/cm^2$ of tensile strength, 19% of swelling ratio, 42% of water uptake, and 56.4% salt removal rate were achieved at best. VA content plays a leading role on the extent of physical properties and performance; however, MI is important for having uniform distribution of resin grains and achieving better ionic conductivity. Overall, manufacturing cost has been suppressed to 5-10% of that of homogeneous ion exchange membranes.

Confirmation of The Fouling Phenomena in CDI Process and The Establishment of Its Removal Process Conditions (CDI 전극 내 파울링 현상 확인 및 제거공정 조건의 확립)

  • Kim, Tae Yeong;Rhim, Ji Won
    • Membrane Journal
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    • v.29 no.5
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    • pp.276-283
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    • 2019
  • In this study, The experiments of the confirmation of the fouling phenomena in CDI process and the establishment of its removal process conditions were carried out. The foulant concentrations of humic acid sodium salt (HA) added to the feed solution were 5, 10, 15 mg/L, respectively. The occurrence of fouling under the certain adsorption/desorption conditions could be confirmed with an increase in adsorption and desorption concentration curve over time. Both the voltage and time in adsorption and desorption processes were changed to eliminate the fouled pollutants. Typically, the fouling removal condition was found at the adsorption condition 1.2 V/5 min and the desorption condition -3 V/2 min, respectively.

Preparation of Anion Exchange Membranes of Cross-linked Poly((vinylbenzyl)trimethylammonium chloride-2-hydroxyethyl methacrylate)/Poly(vinyl alcohol) (가교결합한 Poly((vinylbenzyl)trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) 음이온 교환막 제조)

  • Kim, Mi-Yang;Kim, Kwang-Je;Kang, Ho
    • Applied Chemistry for Engineering
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    • v.21 no.6
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    • pp.621-626
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    • 2010
  • Anion exchange membranes can be used for reverse electrodialysis for electric energy generation, and capacitive deionization for water purification, as well as electrodialysis for desalination. In this study, anion exchange membranes of poly((vinylbenzyl) trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) were prepared through the polymerization of (vinylbenzyl)trimethylammonium chloride and 2-hydroxyethyl methacrylate in aqueous poly(vinyl alcohol) solutions, esterification with glutaric acid, and cross-linking reaction with glutaraldehyde. We investigated electrochemical properties for the anion exchange membranes prepared according to experimental conditions. Ion exchange capacity and electrical resistance for the membranes were changed with a variation in the monomer ratio in polymerization. Water uptake and conductivity for the membranes decreased with an increase in the content of glutaric acid in esterification. The change in the time of crosslinking reaction with the formed film and glutaraldehyde affected electrochemical properties such as water uptake, conductivity, or transport number for the membranes. Chronopotentiometry and limiting current density for the anion exchange membranes prepared were measured.

Preparation and Properties of Sulfonated Polyvinylchloride (PVC) Membrane for Capacitive Deionization Electrode by Ultra Sonication Modification (초음파 표면개질에 의한 CDI 전극용 술폰화 염화비닐(PVC) 멤브레인의 제조 및 특성)

  • Hwang, Chi Won;Oh, Chang Min;Hwang, Taek Sung
    • Journal of Adhesion and Interface
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    • v.15 no.1
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    • pp.1-8
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    • 2014
  • Ion exchange membrane is widely used in various fields such as electro dialysis, diffusion dialysis, redox flow battery, fuel cell. PVC cation exchange membrane using ultrasonic modification was prepared by sulfonation reaction in various sulfonation times. Sulfuric acid was used as a sulfonating agent with ultrasonic condition. We've characterized basic structure of sulfonated PVC cation exchange membrane by FT-IR, EDX, water uptake, ion exchange capacity (IEC), electrical resistance (ER), conductivity, ion transport number and surface morphology (SEM). The presence of sulfonic groups in the sulfonated PVC cation exchange membrane was confirmed by FT-IR. The maximum values of water uptake, IEC, electrical resistance and ion transport number were 40.2%, 0.87 meq/g, $35.2{\Omega}{\cdot}cm^2$ and 0.88, respectively.

Feasibility Study on Double Path Capacitive Deionization Process for Advanced Wastewater Treatment (이단유로 축전식 탈염공정의 하수고도처리 적용가능성 평가)

  • Cha, Jaehwan;Shin, Kyung-Sook;Lee, Jung-Chul;Park, Seung-Kook;Park, Nam-Su;Song, Eui-Yeol
    • Journal of Korean Society of Environmental Engineers
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    • v.36 no.4
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    • pp.295-302
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    • 2014
  • This study demonstrates a double-path CDI as an alternative of advanced wastewater treatment process. While the CDI typically consists of many pairs of electrodes connected in parallel, the new double-path CDI is designed to have series flow path by dividing the module into two stages. The CFD model showed that the double-path had uniform flow distribution with higher velocity and less dead zone compared with the single-path. However, the double-path was predicted to have higher pressure drop(0.7 bar) compared the single-path (0.4 bar). From the unit cell test, the highest TDS removal efficiencies of single- and double-path were up to 88% and 91%, respectively. The rate of increase in pressure drop with an increase of flow rate was higher in double-path than single-path. At 70 mL/min of flow rate, the pressure drop of double-path was 1.67 bar, which was two times higher than single-path. When the electrode spacing was increased from 100 to $200{\mu}m$, the pressure drop of double-path decreased from 1.67 to 0.87 bar, while there was little difference in TDS removal. When proto type double-path CDI was operated using sewage water, TDS, $NH_4{^+}$-N, $NO_3{^-}$-N and $PO_4{^{3-}}$-P removal efficiencies were up to 78%, 50%, 93% and 50%, respectively.